Dispenser type cathode having gettercoated parts



April 10, 1956 H. KATz 2,741,717

DISPENSER TYPE CATHODE HAVING GETTER-COATED PARTS Filed June 9, 1952lmmn-lllllmnm 19 ,iyefgfof afg.

United States Patent DISPENSER TYPE CATHODE HAVING GETTER- COATED PARTSHelmut Katz, Erlangen, Germany, assigner to Siemens &

Halske Aktiengesellschaft, Munich and Berlin, Germany, a Germancorporation type cathodes, for use in electrical discharge devices,having a supply of emissive material which migrates at operatingtemperature through fine passages of a cathode body to the emittingsurface formed thereby.

The object of the invention is to improve the production and operationof discharge devices of the above indicated type by the provision ofgetter substance upon selected parts of the cathode which do not serveelectron emission or upon selected parts of elements connected orassociated with the cathode which are during operation strongly heated.

Discharge devices having incandescible dispenser type cathodes have beenproposed before. The fine passages for the migration of the emissivematerial to the cathode surface may be formed by wire or the like meanswhich is tightly wound about the cathode body or by the pores of asintered cathode body made of materials -such as tungsten or molybdenumwhich are particularly suitable when using thorium or bariumcompositions as emissive materials.

lt was found that it is of great advantage in the manufacture andoperation of tubes of the type indicated above, to provide therein avolatile metal such, for example, as zirconium, which exhibits atoperating temperatures a getter action so as to remove traces of gasremaining after evacuation. Difficulties were, however, encountered inmany cases, for example, in at or disk-shaped cathodes, to select partswhich become in operation hot enough so that the getter provided thereonwould develop a satisfactory action.

The invention solves the problem as indicated before, by providing thegetter on selected parts which do not serve electron emission but aresubjected to strong heating. The getter is disposed so as to avoidinterference with the radiation properties of the cathode.

The invention will be explained with reference to the accompanyingdrawing showing in diagrammatic manner an example thereof.

Numeral 11 indicates a hat or disklike cathode body of sintered tungstenor molybdenum. The emissive material 12 which may be barium or thoriumis disposed in a receptacle 13 having a ange 14 which is suitablysecured to the cathode body 11, for example, by soldering or welding. Atubular supporting member 15 having a ange 16 is similarly secured tothe flange of the receptacle 13. The heater filament 17 is supported bythe rod 18. Numeral 19 indicates a grid, 20 the anode, and 21 to 25 areconnecting and terminal conductors for the various parts. Additionalheater means (not shown) may be provided, for example, in the spacebetween the side wall of the receptacle 13 and the inside wall of thesupporting member 15. The envelope for the discharge tube has beenomitted to avoid encumbering the drawing. It is understood of coursethat the various parts are by known and suitable means secured withinthe tube envelope and that the terminal conductors are carried to theoutside of the tube in vacuumtight manner.

Fice

A getter substance, for example, zirconium, may be disposed on theinside of the tubular supporting member 1S as indicated at 26. Thegetter may also be provided on selected parts'ofthe grid A19, asindicated at 27, and if desired lalso on the rod 18, as indicated by theshading, or on the bottom of the receptacle 13, as indicated at 28. Theside wall of the receptacle 13 may be provided with getter substance ifdesired.

While it is possible to dispose getter substance on all the elementsnoted above, it will suffice for most practical purposes to provide thegetter only on selected parts or portions of some of the elements.

The drawing shows a cylindrical structure having a circular cathode bodyof dat or disklike shape. It is understood of course that the structuremay be crosssectionally rectangular or the like.

Changes may be made within the scope and spirit of the appended claims.

I claim:

l. A dispenser type cathode for use in an electrical discharge devicecomprising a cathode body, a first element having a portion connected tosaid cathode body peripherally on one side thereof and forming therewitha receptacle containing an emissive material, a second tubular elementhaving one end thereof connected to the portion of said first elementwhich is connected to said cathode body peripherally on one ysidethereof and extending axially therefrom, the side of said cathode whichfaces axially away from said elements being entirely exposed and formingthe emitting surface, the inside wall of said tubular second elementsurrounding a portion of the outside Wall of said first element andforming a chamber therewith, a heater filament disposed within saidchamber in spaced relation to each of said elements and means separatefrom said elements for connecting current to said filament to cause itto generate heat within said chamber for transfer substantially byradiation therefrom respectively to said iirst and said second elementsso as to heat said emissive material and said cathode body for thepurpose of causing migration of emissive material from said receptaclethrough said cathode body to the emitting surface formed thereby foremission therefrom substantially over the entire area of said surface,and a getter substance disposed on the side of the wall means of atleast one of said elements which faces said heater filament.

2. A dispenser type cathode for use in an electrical discharge devicecomprising a cathode body, a i'irst element having a portion connectedto said cadaode body peripherally on one side thereof and formingtherewith a receptacle containing an emissive material, a second tubularelement having one end thereof connected to the portion of said firstelement which is connected to said cathode body peripherally on one sidethereof and extending axially therefrom, the side of said cathode bodywhich faces axially away from said elements being entirely exposed andforming the emitting surface, the inside wall of said tubular secondelement surrounding a portion of the outside wall of said first elementand forming a chamber therewith, a heater filament disposed within saidchamber in spaced relation to said elements, a third element formingsupporting member for said heater filament disposed in spaced relationthereto, means separate from said elements for connecting current tosaid filament to cause it to generate heat within said chamber fortransfer substantially by radiation therefrom respectively to said firstand said second and said third elements so as to heat said emissivematerial and said cathode body and also said third element for thepurpose of causing migration of emissive material from said receptaclethrough said cathode body to the emitting surface formed thereby foremission therefrom substantially over the entire area of said surface,and a getter substance disposed on the side of Y the Awall means of atlest one of said lements which faces said heater lament. Y

3. The structure defmed in claim 1, comprising a disk-.like'substaptally frusfo-concal oathode body.

Y ReferencesCtod in the le of this patent Wooten Jan. 23,v 1945 FultonMay 14, 1946 Drggs June 29, 1948 Lockwood et al Sept. 21, 1948 StanierMay 30, 1950 Lemmens et Feb. 27, 1951

1. A DISPENSER TYPE CATHODE FOR USE IN AN ELECTRICAL DISCHARGE DEVICE COMPRISING A CATHODE BODY, A FIRST ELEMENT HAVING A PORTION CONNECTED TO SAID CATHODE BODY PERIPHERALLY ON ONE SIDE THEREOF AND FORMING THEREWITH A RECEPTACLE CONTAINING AN EMISSIVE MATERIAL, A SECOND TUBULAR ELEMENT HAVING ONE END THEREOF CONNECTED TO THE PORTION OF SAID FIRST ELEMENT WHICH IS CONNECTED TO SAID CATHODE BODY PERIPHERALLY ON ONE SIDE THEREOF AND EXTENDING AXIALLY THEREFROM, THE SIDE OF SAID CATHODE WHICH FACES AXIALLY AWAY FROM SAID ELEMENTS BEING ENTIRELY EXPOSED AND FORMING THE EMITTING SURFACE, THE INSIDE WALL OF SAID TUBULAR SECOND ELEMENT SURROUNDING A PORTION OF THE OUTSIDE WALL OF SAID FIRST ELEMENT AND FORMING A CHAMBER THEREWITH, A HEATER FILAMENT DISPOSED WITHIN SAID CHAMBER IN SPACED RELATING TO EACH OF SAID ELEMENTS AND MEANS SEPARATE FROM SAID ELEMENTS FOR CONNECTING CURRENT TO SAID FILAMENT TO CAUSE IT TO GENERATE HEAT WITHIN SAID CHAMBER FOR TRANSFER SUBSTANTIALLY BY RADIATION THEREFROM RESPECTIVELY TO SAID FIRST AND SAID SECOND ELEMENTS SO AS TO HEAT SAID EMISSIVE MATERIAL AND SAID CATHODE BODY FOR THE PURPOSE OF CAUSING MIGRATION OF EMISSIVE MATERIAL FROM SAID RECEPTACLE THROUGH SAID CATHODE BODY TO THE EMITTING SURFACE FORMED THEREBY FOR EMISSION THEREFROM SUBSTANTIALLY OVER THE ENTIRE AREA OF SAID SURFACE, AND A GETTER SUBSTANCE DISPOSED ON THE SIDE OF THE WALL MEANS OF AT LEAST ONE OF SAID ELEMENTS WHICH FACES SAID HEATER FILAMENT. 